With rapid development of wireless communications, a data transmission rate up to dozens of megabits even hundreds of megabits per second is required in a future mobile communications system. With given radio spectrum resources, in a multiple-input multiple-output (MIMO) technology using multiple transmit antennas and multiple receive antennas, by using a spatial degree of freedom, a system capacity and coverage can be improved, a user rate can be increased, and user experience can be improved.
For example, in a distributed 4×2 MIMO networking scenario, two base stations and four antenna ports are configured. Each base station includes two physical antennas. Four antenna port signals may be separately transmitted by using four physical antennas, that is, each physical antenna transmits one antenna port signal. If user equipment is close to one base station and is far from the other base station, downlink propagation path losses of the four physical antennas are different. Consequently, channel powers that are received and used by the user equipment to perform data demodulation are imbalanced, and downlink transmission efficiency is reduced.